Spontaneous retroperitoneal and intracranial hemorrhage following streptokinase therapy in acute myocardial infarction: An autopsy case report.

Bleeding complications following thrombolytic treatment for acute myocardial infarction (AMI) are not infrequent, among which intracranial hemorrhage is commonly reported. In contrast, retroperitoneal hematoma following the administration of thrombolytics is rarely reported in the literature. We are reporting a case of a middle-aged man, who presented with left-sided chest pain and was diagnosed with acute coronary syndrome with anterior wall ST elevation AMI. The patient was administered with thrombolytic drugs, including streptokinase and heparin. Percutaneous coronary intervention in the form of Coronary angioplasty with stent insertion was done to the left anterior descending artery, given coronary artery disease. The blood investigations showed elevated activated partial thromboplastin time and prothrombin time. The patient developed vomiting, altered sensorium, and left-sided weakness, and a non-contrast computerized tomography brain was done, which showed acute hemorrhage involving the right frontal lobe with intraventricular extension, so the ventricular drain was placed. The patient developed cardiac arrest and died on the third day. On autopsy examination, the brain showed subarachnoid hemorrhage, intraparenchymal hemorrhage over the right frontal lobe, and clotted blood in all the ventricles. A retroperitoneal hematoma of around 1500 cc was seen over the left side of the peritoneal cavity. This case highlights that although intracranial hemorrhage is a known complication after administrating thrombolytic therapy, clinicians should also be aware of the possibility of retroperitoneal hemorrhage. This case emphasizes the value of an autopsy in determining the cause of death in such situations.

Magnetic Nanoparticles Mediated Thrombolysis-A Review.

Nanoparticles containing thrombolytic medicines have been developed for thrombolysis applications in response to the increasing demand for effective, targeted treatment of thrombosis disease. In recent years, there has been a great deal of interest in nanoparticles that can be navigated and driven by a magnetic field. However, there are few review publications concerning the application of magnetic nanoparticles in thrombolysis. In this study, we examine the current state of magnetic nanoparticles in the application of in vitro and in vivo thrombolysis under a static or dynamic magnetic field, as well as the combination of magnetic nanoparticles with an acoustic field for dual-mode thrombolysis. We also discuss four primary processes of magnetic nanoparticles mediated thrombolysis, including magnetic nanoparticle targeting, magnetic nanoparticle trapping, magnetic drug release, and magnetic rupture of blood clot fibrin networks. This review will offer unique insights for the future study and clinical development of magnetic nanoparticles mediated thrombolysis approaches.

Comparative Efficacy and Safety of Thrombolytic Agents for Pulmonary Embolism: A Bayesian Network Meta-Analysis.

BACKGROUND: Thrombolytic agents and anticoagulants are the two classes of medication used in the treatment of acute pulmonary embolism (PE). There is continuous renewal and iteration of thrombolytic agents, and the efficacy and adverse effects of different agents have different effects on PE due to their different mechanisms of action. OBJECTIVES: The aim of the study was to evaluate the efficacy and safety of different thrombolytic agents in the treatment of all types of acute PE: hemodynamically unstable PE (massive PE) and hemodynamically stable PE (submassive PE and low-risk PE), using a network meta-analysis. METHODS: A search was conducted of the following databases: PubMed, The Cochrane Library, Embase, and Web of Science to collect randomized controlled trials (RCTs) comparing thrombolytic agents with heparin or other thrombolytic agents in patients with acute PE; the clinical outcomes included patient mortality, recurrent PE, pulmonary artery systolic pressure (PASP) after treatment, and major and minor bleeding. The measurement duration of outcome indicators was the longest follow-up period. Thereafter, a network meta-analysis was performed using a Bayesian network framework. RESULTS: A total of 29 RCTs (3,067 patients) were included, of which 6 studies (304 patients) were massive PE, 14 studies (2,173 patients) were submassive PE, 1 study (83 patients) included massive and submassive PE, and 8 studies (507 patients) were PE of unknown type. The treatment regimens included thrombolytic therapy (alteplase, reteplase, tenecteplase, streptokinase, and urokinase) and anticoagulant therapy alone. The results showed that the mortality using thrombolytic agents (except tenecteplase) was significantly lower compared with heparin. The recurrence of PE with alteplase was significantly lower compared with heparin (RR = 0.23, 95% CI, 0.04, 0.65). The PASP after using alteplase was significantly lower compared with heparin (mean difference = -11.36, 95% CI, -21.45, -1.56). Compared with heparin, the incidence of minor bleeding associated with tenecteplase was higher (RR = 3.27, 95% CI, 1.36, 7.39); compared with streptokinase, the incidence of minor bleeding associated with tenecteplase was higher (RR = 3.22, 95% CI, 1.01, 11.10). CONCLUSION: For patients with acute PE, four thrombolytic agents (alteplase, reteplase, streptokinase, and urokinase) appeared to be superior in efficacy compared with anticoagulants alone due to a reduction in mortality and no increase in bleeding risk. Alteplase may be a better choice because it not only reduced mortality but also reduced PE recurrence rate and treated PASP. Tenecteplase did not reduce mortality compared with anticoagulants alone and may not be a good choice of thrombolytic agent due to an increase in minor bleeding compared with streptokinase and anticoagulants alone. Thrombolytic drugs should be rationally selected to optimize the thrombolytic regimen and achieve as good a balance as possible between thrombolysis and bleeding.

Association Between the Use of Pre- and Post-thrombolysis Anticoagulation With All-Cause Mortality and Major Bleeding in Patients With Pulmonary Embolism.

Objective: To explore the comparative clinical efficacy and safety outcomes of anticoagulation before (pre-) or following (post-) thrombolytic therapy in systemic thrombolytic therapy for pulmonary embolism (PE). Methods: PubMed, the Cochrane Library, EMBASE, EBSCO, Web of Science, and CINAHL databases were searched from inception through 1 May 2021. All randomized clinical trials comparing systemic thrombolytic therapy vs. anticoagulation alone in patients with PE and those that were written in English were eligible. The primary efficacy and safety outcomes were all-cause mortality and major bleeding, respectively. Odds ratios (OR) estimates and associated 95% confidence intervals (CIs) were calculated. A Bayesian network analysis was performed using R studio software, and then the efficacy and safety rankings were derived. Results: This network meta-analysis enrolled 15 trials randomizing 2,076 patients. According to the plot rankings, the anticoagulant therapy was the best in terms of major bleeding, and the post-thrombolysis anticoagulation was the best in terms of all-cause mortality. Taking major bleeding and all-cause mortality into consideration, the most safe-effective treatment was the post-thrombolysis anticoagulation in patients who needed thrombolytic therapy. The net clinical benefit analysis comparing associated ICH benefits vs. mortality risks of post-thrombolysis anticoagulation demonstrated a net clinical benefit of 1.74%. Conclusion: The systemic thrombolysis followed by anticoagulation had a better advantage in all-cause mortality and major bleeding than the systemic thrombolysis before anticoagulation. The adjuvant anticoagulation treatment of systemic thrombolytic therapy should be optimized.

Acute Ischemic Stroke With Mild Symptoms-To Thrombolyse or Not to Thrombolyse?

Management of stroke with minor symptoms may represent a therapeutical dilemma as the hemorrhage risk of acute thrombolytic therapy may eventually outweigh the stroke severity. However, around 30% of patients presenting with minor stroke symptoms are ultimately left with disability. The objective of this review is to evaluate the current literature and evidence regarding the management of minor stroke, with a particular emphasis on the role of IV thrombolysis. Definition of minor stroke, pre-hospital recognition of minor stroke and stroke of unknown onset are discussed together with neuroimaging aspects and existing evidence for IV thrombolysis in minor strokes. Though current guidelines advise against the use of thrombolysis in those without clearly disabling symptoms due to a paucity of evidence, advanced imaging techniques may be able to identify those likely to benefit. Further research on this topic is ongoing.

Effects of Intracoronary Pro-urokinase or Tirofiban on Coronary Flow During Primary Percutaneous Coronary Intervention for Acute Myocardial Infarction: A Multi-Center, Placebo-Controlled, Single-Blind, Randomized Clinical Trial.

Background: To determine whether intracoronary pro-urokinase or tirofiban improves myocardial reperfusion during primary percutaneous coronary intervention (PCI) for acute ST-segment elevation myocardial infarction (STEMI). Methods: The study included patients with acute STEMI presenting within 12 h of symptoms at 11 hospitals in China between November 2015 and July 2017. Patients were randomized to receive selective intracoronary infusion of recombinant pro-urokinase (20 mg), tirofiban (10 µg/kg), or saline (20 mL) proximal to the infarct-related lesion over a 3-min period before stent implantation during primary PCI. The primary outcome was final corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) after PCI. Results: This study included 345 patients. Initial angiography identified a high-grade thrombus (TIMI 4-5) in 80% of patients. Final CTFC after PCI was significantly lower in the pro-urokinase (P < 0.001) and tirofiban (P < 0.001) groups than in the saline group and similar between the pro-urokinase and tirofiban groups (P > 0.05). The pro-urokinase (P = 0.008) and tirofiban groups (P = 0.022) had more complete ST-segment resolution at 2 h and lower peak creatine kinase-MB levels after PCI than the saline group (P = 0.006 and P = 0.023). The 30-day incidence of major adverse cardiac events was 4.5% in the pro-urokinase group, 3.4% in the tirofiban group, and 2.6% in the saline group. The incidence of in-hospital TIMI major bleeding events was low and comparable between groups. Conclusions: Adjunctive intracoronary pro-urokinase or tirofiban given before stent implantation during primary PCI improves myocardial reperfusion without increasing the incidence of major bleeding events.

Inference from longitudinal laboratory tests characterizes temporal evolution of COVID-19-associated coagulopathy (CAC).

Temporal inference from laboratory testing results and triangulation with clinical outcomes extracted from unstructured electronic health record (EHR) provider notes is integral to advancing precision medicine. Here, we studied 246 SARS-CoV-2 PCR-positive (COVIDpos) patients and propensity-matched 2460 SARS-CoV-2 PCR-negative (COVIDneg) patients subjected to around 700,000 lab tests cumulatively across 194 assays. Compared to COVIDneg patients at the time of diagnostic testing, COVIDpos patients tended to have higher plasma fibrinogen levels and lower platelet counts. However, as the infection evolves, COVIDpos patients distinctively show declining fibrinogen, increasing platelet counts, and lower white blood cell counts. Augmented curation of EHRs suggests that only a minority of COVIDpos patients develop thromboembolism, and rarely, disseminated intravascular coagulopathy (DIC), with patients generally not displaying platelet reductions typical of consumptive coagulopathies. These temporal trends provide fine-grained resolution into COVID-19 associated coagulopathy (CAC) and set the stage for personalizing thromboprophylaxis.

Thrombolytic Agents: Nanocarriers in Controlled Release.

Thrombosis is a life-threatening pathological condition in which blood clots form in blood vessels, obstructing or interfering with blood flow. Thrombolytic agents (TAs) are enzymes that can catalyze the conversion of plasminogen to plasmin to dissolve blood clots. The plasmin formed by TAs breaks down fibrin clots into soluble fibrin that finally dissolves thrombi. Several TAs have been developed to treat various thromboembolic diseases, such as pulmonary embolisms, acute myocardial infarction, deep vein thrombosis, and extensive coronary emboli. However, systemic TA administration can trigger non-specific activation that can increase the incidence of bleeding. Moreover, protein-based TAs are rapidly inactivated upon injection resulting in the need for large doses. To overcome these limitations, various types of nanocarriers have been introduced that enhance the pharmacokinetic effects by protecting the TA from the biological environment and targeting the release into coagulation. The nanocarriers show increasing half-life, reducing side effects, and improving overall TA efficacy. In this work, the recent advances in various types of TAs and nanocarriers are thoroughly reviewed. Various types of nanocarriers, including lipid-based, polymer-based, and metal-based nanoparticles are described, for the targeted delivery of TAs. This work also provides insights into issues related to the future of TA development and successful clinical translation.

Assessing Full Benefit of Rivaroxaban Prophylaxis in High-Risk Ambulatory Patients with Cancer: Thromboembolic Events in the Randomized CASSINI Trial.

Introduction In the CASSINI study, rivaroxaban thromboprophylaxis significantly reduced primary venous thromboembolism (VTE) endpoints during the intervention period, but several thromboembolic events designated as secondary efficacy endpoints were not included in the primary analysis. This study was aimed to evaluate the full impact of rivaroxaban thromboprophylaxis on all prespecified thromboembolic endpoints occurring on study. Methods CASSINI was a double-blind, randomized, placebo-controlled study in adult ambulatory patients with cancer at risk for VTE (Khorana score ≥2). Patients were screened at baseline for deep-vein thrombosis (DVT) and randomized if none was found. The primary efficacy endpoint was a composite of lower extremity proximal DVT, symptomatic upper extremity, or lower extremity distal DVT, any pulmonary embolism, and VTE-related death. This analysis evaluated all prespecified thromboembolic endpoints occurring on study to determine the full benefit of rivaroxaban prophylaxis. All endpoints were independently adjudicated. Results Total thromboembolic events occurred in fewer patients randomized to rivaroxaban during the full study period (29/420 [6.9%] and 49/421 [11.6%] patients in rivaroxaban and placebo groups, respectively [hazard ratio (HR) = 0.57; 95% confidence interval (CI): 0.36-0.90; p = 0.01]; number needed to treat [NNT] = 21). Similarly, fewer patients randomized to rivaroxaban experienced thromboembolism during the intervention period (13/420 [3.1%] patients) versus placebo (38/421 [9.0%] patients; HR = 0.33; 95% CI: 0.18-0.62; p < 0.001; NNT = 17). Conclusion Our findings confirm the substantial benefit of rivaroxaban thromboprophylaxis when considering all prespecified thromboembolic events, even after excluding baseline screen-detected DVT. The low NNT, coupled with prior data demonstrating a high number needed to harm, should assist clinicians in determining the risk/benefit of thromboprophylaxis in high-risk patients with cancer.

Hormones, Blood Products, and Therapeutic Enzymes.

Therapeutic uses of biological medicines are diverse and include active substances from different classes. This chapter provides an overview on the clinical applications of biological medicines containing hormones, blood products, and therapeutic enzymes. Currently, therapeutic hormones have 78 approved medicines, including insulin and analogs, glucagon and analogs, growth hormone, gonadotropins (follicle-stimulating hormone, luteinizing hormone, and human chorionic gonadotropin), thyroid-stimulating hormone, and parathyroid hormone. In contrast, recombinant blood products, and particularly blood factors, anticoagulants, and thrombolytic agents, incorporate 49 approved biological medicines. Regarding recombinant therapeutic enzymes, there are 22 approved medicines. Among the referred biological medicines, there are six biosimilar hormones, and no biosimilars have been approved for recombinant blood products and therapeutic enzymes, which is unexpected.Current investigations on recombinant hormones, recombinant blood products, and therapeutic enzymes seem to follow the same directions, searching for alternative non-injectable administration routes, development of new recombinant molecules with improved pharmacokinetic properties and discovering new clinical applications for approved medicines. These approaches are showing positive results and new medicines are expected to reach clinical approval in the coming years. Future prospects also include the approval of more biosimilar medicines.

Improving fibrinolysis in venous thromboembolism: impact of fibrin structure.

Introduction. Fibrinolysis is of key importance in maintaining vessel patency. Impaired fibrinolysis associated with more compact fibrin structure has been shown in patients with venous thromboembolism (VTE), including deep-vein thrombosis and pulmonary embolism (PE). Currently, recombinant or modified plasminogen activators are the only commonly available thrombolytic agents. However, they are fraught with side effects and suboptimal effectiveness. Areas covered. Based on the available literature, the current evidence linking fibrinolysis with VTE and potential therapeutic targets among fibrinolysis proteins are presented. Expert opinion. Prolonged clot lysis time has been reported as a new predictor of first-time and recurrent VTE, including PE. Anticoagulant therapy, including non-vitamin K antagonist oral anticoagulants, has a favorable impact on fibrinolysis in VTE patients. Several VTE risk factors are also related to lower efficiency of fibrinolysis and their treatment improve fibrinolysis, in part by alterations to fibrin properties. There is an increasing number of studies aiming at developing novel profibrinolytic therapeutic agents for treatment of VTE patients, mostly targeting the antifibrinolytic proteins, i.e. antiplasmin, plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor.

Lipid modification of staphylokinase and its implications on stability and activity.

Thrombolytic agents are routinely used to dissolve blood clot by activating fibrinolytic system. Among different thrombolytic agents available, staphylokinase (SAK) is gaining much attention because of their fibrin specificity and reduced inhibition by α2 antiplasmin. Though SAK had exhibited less circulatory half life, they are equipotent to tissue plasminogen activator and streptokinase and had shown more potency for clot dissolution during retracted thrombi. In this study, SAK was lipid modified at the N-terminal by a protein engineering approach to enhance its stability and activity. Native SAK as well as the gene encoding SAK with lipobox was cloned into E. coli GJ1158 using pRSET-B expression vector for higher expression. The lipid modification of SAK was confirmed by a mobility shift of 1.3 kDa against the 15.5 kDa of native SAK using tricine SDS-PAGE. Lipid modification of SAK was confirmed by LC MS/MS. The secondary structure analysis was carried out using circular dichroism and deconvoluted fourier transform infrared spectroscopy. LMSAK was found to have a slightly higher denaturation temperature compared to SAK. The improved stablility and activity of lipid modified SAK was studied by heated plasma agar plate assay and mouse tail bleeding test.

Post-thrombotic syndrome and recurrent thromboembolism in patients with upper extremity deep vein thrombosis: A systematic review and meta-analysis.

INTRODUCTION: There is limited data on the occurrence of complications in patients with upper extremity deep vein thrombosis (UEDVT). AIMS: We aimed to determine the frequency of post-thrombotic syndrome (PTS), thrombosis recurrence and major bleeding (MB) in patients with UEDVT. MATERIAL AND METHODS: We conducted a systematic review of the literature including studies from 1970 onwards. We included observational studies, randomized trials, or cases series including >20 patients. We calculated pooled proportions using a random effects model. Subgroup analyses according to etiology and treatment modality were conducted. RESULTS: A total of 62 studies comprising 3550 patients were included. The pooled proportions for PTS and recurrence were 19.4% (95% CI 11.3-27.6) and 7.5% (95% CI 4.1-10.9), respectively. With a mean follow up of 6 months, the proportion of PTS was higher in patients with primary (unprovoked) UEDVT compared to secondary, whereas recurrence was higher in secondary UEDVT. PTS was more frequent in patients treated with anticoagulation alone compared to thrombolysis or surgical decompression. The pooled proportion for MB was 5.0% (95% CI 0.3-9.7) after anticoagulation alone and 3.8% (95% CI: 2.4-5.8%) after thrombolysis and/or surgery. CONCLUSIONS: This study suggests that UEDVT is associated with significant rates of PTS and recurrence and its treatment has a relatively low risk of major bleeding. Differences exist depending on etiology and treatment modality.

Comparison of alteplase and urokinase for pharmacomechanical thrombolysis of clotted hemodialysis access.

BACKGROUND: Percutaneous pharmacomechanical thrombolysis is increasingly used to salvage thrombosed hemodialysis access. We aim to evaluate the effectiveness of alteplase compared to urokinase in percutaneous pharmacomechanical thrombolysis clotted access. METHODS: Records of patients who underwent pharmacomechanical thrombolysis at Interventional Nephrology Suite in a tertiary teaching hospital from 1 January 2016 to 31 December 2016 were reviewed. Technical and clinical success rates, thrombosis-free and cumulative survivals, procedure time, and radiation dose imparted to patients were compared for pharmacomechanical thrombolysis with urokinase versus alteplase. RESULTS: A total of 122 incident patients underwent pharmacothrombolysis (n = 53 for urokinase, n = 69 for alteplase) during the study period. The mean dose of urokinase and alteplase used was 176,897 ± 73,418 units and 3.7 ± 0.8 mg, respectively. Pharmacomechnical thrombolysis using urokinase versus alteplase has similar technical success rate (98.1% vs 97.1%, p = 0.599), clinical success rate (88.7% vs 97.1%, p = 0.068), complication rate (9.4% vs 13.0%, p = 0.373), and primary patency rates at 3 months (57.1% vs 70.1%, p = 0.106). Thrombosis-free survivals of the vascular access were 113.2 (35.3, 196) days versus 122 (84, 239) days (p = 0.168). Cumulative survivals were 239 (116, 320) vs 213 (110.5, 316.5) days (p = 0.801). Procedure time, fluoroscopy time, skin dose, and dose were significantly lower for pharmacomechanical thrombolysis using alteplase compared to urokinase (p = 0.045, p < 0.0001, p = 0.006, p = 0.001, respectively). Stenting was found to be associated with successful dialysis following thrombolysis on univariate analysis (odds ratio: 9.167, 95% confidence interval: 1.391-19.846, p = 0.021), although this was no longer significant in multivariate analysis (p = 0.078). CONCLUSION: Alteplase is an effective and safe alternative to urokinase for pharmacomechanical thrombolysis of clotted vascular access.

Fibrinolytic Protease from Marine Streptomyces rubiginosus VITPSS1.

INTRODUCTION: Fibrinolytic enzymes must currently originate a significant product in the arena of medical research. Very limited studies are stated on fibrinolyticenzyme production from actinomycetes. METHODS: Streptomyces sp. isolated from marine soil was chosen to optimize its fibrinolytic protease production.16s rRNA sequencing confirmed the isolated potent strain to be Streptomyces rubiginosus VITPSS1. A fibrinolytic protease was then purified from Streptomyces rubiginosus VITPSS1, with the target of producing a cost effective feasible enzyme from a potential actinomycete. RESULTS: SDS-PAGE results exhibited a protein band of about 45 kDa and the fibrinolytic band was detected by zymography. Optimization of physical and nutritional parameters for fibrinolytic protease production from a marine soil isolate Streptomyces strain was done by response surface methodology. The optimal cultural condition for fibrinolytic protease production was obtained with response surface methodology was based on OFAT results, it was inferred that glycerol, Soyabean meal, pH 7.2 and temperature 37°C. The optimization of the production of fibrinolytic protease with response surface methodology bring about two-folds increase in production by Streptomyces rubiginosus VITPSS1. CONCLUSION: Thus, this study presents its novelty by highlighting the potential of marine Streptomyces as a significant source for fibrinolytic enzyme production.

Preventing intraluminal occlusion in peripherally inserted central catheters.

Peripherally inserted central catheters (PICCs) are used in a variety of specialties. Infective and thrombotic complications are widely reported but little has been written about the complications of persistent withdrawal occlusion (PWO) or complete luminal occlusion in PICCs. An audit was conducted of all patients who had a PICC in situ for a 6-week period, using a combination of reviewing clinical documentation and local departmental databases, physical review of inpatients and discussion with the relevant clinical nurse specialists in haematology, oncology, outpatient antibiotic therapy and the vascular access team, to determine the degree of PWO or occlusion but also to review possible financial implications in the introduction of a more expensive product. It was difficult to determine a rate for either PWO or complete occlusion owing to the diversity of the patient cohort and the tertiary nature of the organisation; the occlusion rate was estimated at 5%, but there was general agreement this was underestimating the problem. A needle-free connector was subsequently introduced for all PICCs in haematology, oncology and hepatobiliary services. Following the change in needle-free connector, 180 PICCs were inserted by the vascular access team on one of the organisation's sites over a 12-month period, with a total dwell time of 9702 catheter days (mean: 53.9 days, median: 35 days), a PWO rate of 1/1000 catheter days and total occlusion rate of 0.4/1000 catheter days. The time for insertion to complication of PWO or occlusion ranged from 9 to 144 days. Despite poor baseline data the results suggested the introduction of the bi-directional needle-less connector had a positive impact on the PWO and occlusion rates in PICCs.

Structural basis of specific inhibition of tissue-type plasminogen activator by plasminogen activators inhibitor-1.

Thrombosis is a leading cause of death worldwide [1]. Recombinant tissue-type plasminogen activator (tPA) is the FDA-approved thrombolytic drug for ischemic strokes, myocardial infarction and pulmonary embolism. tPA is a multi-domain serine protease of the trypsin-family [2] and catalyses the critical step in fibrinolysis [3], converting the zymogen plasminogen to the active serine protease plasmin, which degrades the fibrin network of thrombi and blood clots. tPA is rapidly inactivated by endogenous plasminogen activators inhibitor-1 (PAI-1) [4] (Fig. 1). Engineering on tPA to reduce its inhibition by PAI-1 without compromising its thrombolytic effect is a continuous effort [5]. Tenecteplase (TNK-tPA) is a newer generation of tPA variant showing slower inhibition by PAI-1 [6]. Extensive studies to understand the molecular interactions between tPA and PAI-1 have been carried out [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], however, the precise details at atomic resolution remain unknown. We report the crystal structure of tPA·PAI-1 complex here. The methods required to achieve these data include: (1) recombinant expression and purification of a PAI-1 variant (14-1B) containing four mutations (N150H, K154T, Q319L, and M354I), and a tPA serine protease domain (tPA-SPD) variant with three mutations (C122A, N173Q, and S195A, in the chymotrypsin numbering) [19]; (2) formation of a tPA-SPD·PAI-1 Michaëlis complex in vitro [19]; and (3) solving the three-dimensional structure for this complex by X-ray crystallography [deposited in the PDB database as 5BRR]. The data explain the specificity of PAI-1 for tPA and uPA [19], [20], and provide structural basis to design newer generation of PAI-1-resistant tPA variants as thrombolytic agents [19].

Evaluation of the in vivo thrombolytic activity of a metalloprotease from Bothrops atrox venom using a model of venous thrombosis.

BACKGROUND: Due to the importance of blood coagulation and platelet aggregation in brain- and cardiovascular diseases, snake venom proteins that interfere in these processes have received significant attention in recent years considering their potential to be used as models for new drugs. OBJECTIVES: This study aimed at the evaluation of the in vivo thrombolytic activity of Batroxase, a P-I metalloprotease from Bothrops atrox venom. METHODS: In vivo thrombolytic activity of Batroxase was tested on a model of venous thrombosis in rats, with partial stenosis of the inferior vena cava, and vessel wall injury with ferric chloride at 10% for 5 min. After formation of the thrombus, increasing amounts of Batroxase were administered intravenously. The prescription medication Alteplase (tissue-type plasminogen activator) was used as positive control for thrombolytic activity, while saline was used as negative control. Bleeding time was assessed with a tail bleeding assay. RESULTS: Batroxase presented thrombolytic activity in vivo in a concentration-dependent manner, with 12 mg/kg of the metalloprotease causing a thrombus reduction of 80%, a thrombolytic activity very similar to the one observed for the positive control Alteplase (85%). The tail bleeding time was not altered by the administration of Batroxase, while it increased 3.5 times with Alteplase. Batroxase presented fibrinolytic and fibrinogenolytic activities in vitro, which were inhibited by alpha 2-macroglobulin. CONCLUSION: Batroxase presents thrombolytic activity in vivo, thus demonstrating a possible therapeutic potential. The inactivation of the metalloprotease by alpha 2-macroglobulin may reduce its activity, but also its potential side effects, as seen for bleeding time.

Development and characterization of highly selective target-sensitive liposomes for the delivery of streptokinase: in vitro/in vivo studies.

Streptokinase is one of the most commonly used thrombolytic agents for the treatment of thromboembolism. Short half-life of the streptokinase requires administration of higher dose which results in various side effects including systemic haemorrhage due to activation of systemic plasmin. To increase the selectivity of the streptokinase and hence to reduce side effects, various novel carriers have been developed. Among these carriers, liposomes have been emerged as versatile carrier. In the present study, highly selective target-sensitive liposomes were developed and evaluated by in vitro and in vivo studies. Prepared liposomes were found to release streptokinase in vitro following binding with activated platelets. Intravital microscopy studies in thrombosed murine model revealed higher accumulation of liposomes in the thrombus area. In vivo thrombolysis study was performed in the human clot inoculated rat model. Results of the study showed that target-sensitive liposomes dissolved 28.27 ± 1.56% thrombus as compared to 17.18 ± 1.23% of non-liposomal streptokinase. Further, it was also observed that target-sensitive liposomes reduced the clot dissolution time as compared to streptokinase solution. Studies concluded that developed liposomes might be pragmatic carriers for the treatment of thromboembolism.

Crystal Structure of the Michaelis Complex between Tissue-type Plasminogen Activator and Plasminogen Activators Inhibitor-1.

Thrombosis is a leading cause of death worldwide. Recombinant tissue-type plasminogen activator (tPA) is the Food and Drug Administration-approved thrombolytic drug. tPA is rapidly inactivated by endogenous plasminogen activator inhibitor-1 (PAI-1). Engineering on tPA to reduce its inhibition by PAI-1 without compromising its thrombolytic effect is a continuous effort. Precise details, with atomic resolution, of the molecular interactions between tPA and PAI-1 remain unknown despite previous extensive studies. Here, we report the crystal structure of the tPA·PAI-1 Michaelis complex, which shows significant differences from the structure of its urokinase-type plasminogen activator analogue, the uPA·PAI-1 Michaelis complex. The PAI-1 reactive center loop adopts a unique kinked conformation. The structure provides detailed interactions between tPA 37- and 60-loops with PAI-1. On the tPA side, the S2 and S1ß pockets open up to accommodate PAI-1. This study provides structural basis to understand the specificity of PAI-1 and to design newer generation of thrombolytic agents with reduced PAI-1 inactivation.